1. Field of the Invention
The field of art to which this invention pertains is that of tire inspection and more particularly relates to a defect marker method and apparatus for use with tire inspection machines, for example x-ray machines, used for the inspection of the internal construction of tires.
2. Description of the Prior Art
X-ray tire inspection systems are currently in use in which a tire manipulator supports a tire for rotation about its center line while an x-ray source is positioned within the torus defined by the tire. X-rays are then directed through an adjacent circumferential section of the tire in a manner well known in the art. Such system generally employ imaging units which move along orbital or arcuate paths about the exterior of the circumferential tire section to produce x-ray transparency images of the internal construction of the tire. These images are then viewed by a camera which transmits the images to a remote display screen such as a cathode ray tube monitor in an operator's booth.
This general system of inspecting tires by x-raying them has proven beneficial in locating defects not readily discernible by other means. However, it has been and continues to be difficult to pinpoint the actual location of a defect when it is observed on the remote monitor. U.S. Pat. No. 3,789,226 discloses an x-ray tire inspection machine wherein an ink spray head is located just outside of the x-ray beam. When an operator sees a defect, he actuates a reject control button that will cause an ink spray to discharge a bright colored ink on the part of the tire corresponding to the image displayed on the monitor which, however, is the part adjacent to that momentarily in the x-ray beam. Thus a segment of the tire visualized on the monitor is no longer in the axis of the imaging system but is one step removed. A related method is taught in U.S. Pat. No. 2,301,251 wherein the tire being inspected is marked at a point of defect by means of marking fluid that is projected by air under pressure. It should be noted that neither of these methods is very accurate and U.S. Pat. No. 3,789,226 even notes that the marking and subsequent diversion of the tire is to permit further inspection and repair or final rejection. In addition, spraying is environmentally detrimental to the imaging screen of the inspection machine.
U.S. Pat. No. 2,220,246 discloses a rather rudimentary inspection device wherein a defect on the tire is marked by physically actuating a marking means which places a scuff mark on the tire. Similarly, U.S. Pat. No. 2,272,893 discloses a tire inspection apparatus wherein, when a defect is found in the tire, the position may be marked via a marking means which could be chalk or crayon.
U.S. Pat. No. 3,952,194 utilizes an elastic band, having numerals thereon spaced equally around same to identify the location of a defect in a tire when the x-ray image appears on the cathode monitor so as to relate the defect discovered in the tire relative to the indicia visible on the monitor.
A further prior art method of identifying a defect includes shutting down of the x-ray machine by the operator and then physically adding a thumbtack in the approximate area of the defect and then reactivating the x-ray machine to check the location of the thumbtack relative to the defect itself.
Thus there appears to be a very definite need for precisely and accurately marking a defect in real time, i.e., while the tire is actually being viewed on the monitor. For some time, efforts have been directed toward overcoming the previously described difficulties and toward producing an improved marking device capable of rapid and accurate marking of defects within the tire construction that are not subject to the previously described disadvantages. The method and apparatus of this invention constitutes a successful culmination of such efforts.